diff options
| -rw-r--r-- | Lisp/policy.lisp | 79 |
1 files changed, 77 insertions, 2 deletions
diff --git a/Lisp/policy.lisp b/Lisp/policy.lisp index 71f7795..64ace7d 100644 --- a/Lisp/policy.lisp +++ b/Lisp/policy.lisp @@ -18,8 +18,45 @@ (in-package #:mulk.objective-cl) -;; FIXME: Document. (defun define-returns-boolean-exception (selector-designator) + "Define an exception to the rule that `char` means `BOOL` as a method return type. + +## Arguments and Values: + +*selector-designator* --- a *selector designator*. + + +## Description: + +Normally, Objective-C treats method return values that are nominally of +type `char` as booleans and converts them to either __t__ or __nil__ +depending on whether they are __zerop__. +__define-returns-boolean-exception__ directs Objective-CL to treat +`char` values returned by methods named by *selector-designator* as +numbers instead. + +__undefine-returns-boolean-exception__ restores the default behaviour. + + +## Examples: + + (define-returns-boolean-exception \"charValue\") + (define-returns-boolean-exception \"characterAtIndex:\") + + +## Rationale: + +The Objective-C runtime offers no way of distinguishing booleans from +chars, even though Foundation defines a `BOOL` type. In the vast +majority of cases, `char` therefore actually means `BOOL`, but the +`NSString` class, for one, wouldn't always agree with that sentiment, so +the only sane way of handling both booleans and actual `char` values is +to determine the intentional type by method selector. + + +## See also: + + __undefine-returns-boolean-exception__" (let ((key (typecase selector-designator (string selector-designator) (t (selector-name (selector selector-designator)))))) @@ -27,7 +64,45 @@ ;; FIXME: Document. -(defun undefine-returns-boolean-exceptions (selector-designator) +(defun undefine-returns-boolean-exception (selector-designator) + "Revert the effect of __define-returns-boolean-exception__ for a given selector. + +## Arguments and Values: + +*selector-designator* --- a *selector designator*. + + +## Description: + +Normally, Objective-C treats method return values that are nominally of +type `char` as booleans and converts them to either __t__ or __nil__ +depending on whether they are __zerop__. +__define-returns-boolean-exception__ directs Objective-CL to treat +`char` values returned by methods named by *selector-designator* as +numbers instead. + +__undefine-returns-boolean-exception__ restores the default behaviour. + + +## Examples: + + (undefine-returns-boolean-exception \"boolValue\") + (undefine-returns-boolean-exception \"isEqual:\") + + +## Rationale: + +The Objective-C runtime offers no way of distinguishing booleans from +chars, even though Foundation defines a `BOOL` type. In the vast +majority of cases, `char` therefore actually means `BOOL`, but the +`NSString` class, for one, wouldn't always agree with that sentiment, so +the only sane way of handling both booleans and actual `char` values is +to determine the intentional type by method selector. + + +## See also: + + __define-returns-boolean-exception__" (let ((key (typecase selector-designator (string selector-designator) (t (selector-name (selector selector-designator)))))) |